The invention is based on an actuating unit.
An actuating unit of this kind for a wheel brake of a motor vehicle has already been disclosed (EP 0 025 714 A1), in which a hydraulic pump that is driven by an electric motor aspirates pressure fluid from a storage tank and feeds it into a high-pressure reservoir. During a braking maneuver, by means of an electrical brake request signal, an electronic control unit switches an electromagnetically actuatable directional-control valve and introduces brake pressure into a cylinder-piston unit in order to press a brake lining against a friction element connected to a vehicle wheel. Since the directional-control valve can only be switched between a pressure increase position and a pressure decrease position, an approximate pressure maintenance can only be achieved by continuously switching the valve between its two positions and therefore brake pressure modulation is not very convenient. In addition, the pressure fluid storage tank requires additional installation space in the actuating unit.